Ultrasound-guided interventional procedures such as breast biopsies and prostate brachytherapy are well-known. Needles can be inserted into the body and either obtain a biopsy sample or deliver a dose of a selected therapy. For biopsies, it is desirable to target a specific volume when obtaining a tissue sample. Where a dose is being administered to a target volume, it is desirable to track the precise location of the needle delivering the dose in real-time to ensure that the therapy is delivered according to plan.
Radioactive seeds can be used as a therapy to treat tumors in prostates. In order to ensure adequate coverage of the therapy, it is desirable to implant the seeds a pre-determined distance apart if the distance between the seeds is too large, tissue between the seeds may not receive the amount of therapy needed for the treatment. If, instead, the seeds are too closely positioned, the tissue can be over-exposed. Further, it is desirable to ensure that the implantation of the seeds is limited to the target volume in order to prevent the therapy from adversely affecting otherwise healthy tissue.
In robotic-aided interventional procedures, such as robot-aided and ultrasound-guided prostate brachytherapy as well as free-hand ultrasound-guided biopsy procedures, a needle is inserted free from parallel trajectory constraints. Oblique insertion of the needle, however, can result in the needle intersecting the two-dimensional (“2D”) trans-rectal ultrasound (“TRUS”) image and appearing as a point, leading to blind guidance.
Some investigators have developed automatic needle segmentation methods to locate needles for biopsies and therapy. These methods, however, require that the needle be completely contained in the 2D ultrasound (“US”) image.
The general operation of ultrasound transducers has provided less-than-desirable image resolution in some instances. Image quality for less significant regions distal from the target volume or even along the shaft of the needles may not be as critical as for the region surrounding the needles. This is especially true for therapy where seeds are being implanted in a target volume. Current ultrasound techniques, however, are directed to the capture of generally evenly distributed images, regardless of the content of the volume targeted by the images.
It is, therefore, an object of the present invention to provide a novel method of imaging using an ultrasound imaging system.